The present invention relates to a device for quick coupling a tube to a rigid element.
Quick coupling devices of the xe2x80x9ccartridgexe2x80x9d type are known for making a leakproof connection of a tube in a bore of a rigid element such as the body of a hydraulic or a pneumatic component. In general, this kind of coupling comprises a tubular insert possessing external means for fixing it in a housing of the rigid element and internal means for locking the tube in the insert, a sealing gasket being disposed between the tube and the housing of the rigid element.
In the most widespread quick coupling devices, the insert is screwed into tapping in the bore of the rigid element and the tube is locked by a deformable anchoring washer having radial claws which xe2x80x9cbitexe2x80x9d into the outside face of the tube.
The tube is generally not rigidly held in an axial direction in this type of coupling for the following reasons. Firstly, functional clearance can exist between the claw washer and the insert itself. In addition, and above all, the claws are flexible blades which, when traction is applied on the tube, are subjected to elastic buckling such that the greater the traction, the greater the deformation of the teeth, and the greater the axial displacement of the tube relative to the insert.
In fact, the traction force on the tube is generated by the pressure that exists inside the circuit to which the tube belongs. Some circuits are continuously under constant pressure. The tube takes up its position in the insert and under such circumstances couplings with claws are quite satisfactory. In other circuits, pressure varies over a large amplitude range, and sometimes at high frequency. This applies in particular to motor vehicle braking circuits fitted with systems for preventing the brakes locking.
Under those conditions of use, claw couplings present drawbacks. Each claw is subjected to buckling fatigue stress which reduces the lifetime of the ring. In addition, the inside volume of the circuit is not constant since the tube moves relative to the insert under the effect of pressure variations, and that can disturb the operation of certain devices served by the circuit, and in particular devices for preventing brakes from locking. In brake circuit applications, operating pressures can have peak values lying in the range 100 bars to 350 bars, with pulsations at 15 Hertz (Hz).
An object of the invention is to design a quick coupling device in which tube locking in the axial direction is very rigid against forces for withdrawing the tube so that play in the withdrawal direction, if not zero, is at least fixed and predetermined.
According to the invention, this object is achieved by a quick coupling device for coupling a tube to a rigid element, the device comprising a tubular insert possessing external means for fixing it in a bore in the rigid element and internal means for axially locking the tube in the insert opposing at least extraction of the tube, wherein the axial locking means comprise a sleeve placed inside the tubular insert and possessing at least a broad cross-section arranged to bear against an internal abutment member of the tubular insert and a narrow cross-section that is elastically deformable in a radial direction between a rest configuration that is small enough to form an abutment for a shoulder of the tube, such that the sleeve forms a spacer opposing withdrawal of the tube after it has been inserted, and an elastically deformed configuration where it is expanded to enable the shoulder of the tube to pass through during insertion thereof.
In operation, the sleeve is thus interposed between the shoulder of the tube and the internal abutment member of the insert to form a positive abutment for rigidly retaining the tube in the insert. On assembly, the tube is inserted into the insert by radial elastic expansion of the deformable section of the sleeve allowing the shoulder of the tube to pass through. Once this shoulder of the tube has gone past the deformable section of the sleeve, the sleeve retracts behind the shoulder to form an abutment that opposes withdrawal of the tube. Withdrawal forces exerted axially on the tube are thus taken up between the shoulder of the tube and the internal abutment member of the insert by means of the sleeve which forms an undeformable spacer.
In an advantageous embodiment of the sleeve, the broad and narrow sections of the sleeve are situated at its ends. The sleeve has an internal passage that converges continuously from its broad end towards its narrow end. The broad end of the sleeve has a cross-section that is polygonal in shape, while the narrow end of the sleeve has a cross-section made up of a succession of circular arcs whose intersections are connected to the vertices of the polygonal section of the broad end by substantially longitudinal ridges between which the sleeve presents curved outside facets. This provides a sleeve having intrinsic capacity for elastic deformation in the radial direction, while presenting small radial size, and also good resistance to compression. The longitudinal ridges further reinforce the compression strength of the sleeve and oppose buckling thereof.
Advantageously, the sleeve is made as a steel swaging. The sleeve thus presents good characteristics of elasticity and mechanical strength, while being particularly simple and inexpensive to manufacture.
The shoulder of the tube can be constituted by a bearing flank of a neck formed in the outer surface of the tube or of a bead formed on the tube.
The abutment member of the tubular insert can be made in the form of a simple internal shoulder or indeed in the form of a groove having the broad end of the sleeve crimped therein. In the second case, the broad end of the sleeve can be spread outwards to form a collar which is crimped in the groove of the sleeve.
The invention also provides a cartridge for packaging the insert and the sleeve, the cartridge comprising an inner retention sheath having a portion received inside the tubular insert, a guard forming a plug for closing one end of the tubular insert, and at least two elastically flexible branches having respective free ends extending beyond the other end of the insert and fitted with radial projections for retaining the sleeve inside the insert.
Advantageously, between the projecting ends of the branches of the sheath and the insert, the cartridge comprises a washer whose inside diameter is less than the inside diameter of the insert at the corresponding end and whose outside diameter is no greater than the outside diameter of the insert at said end. The washer has at least three resilient tabs that can be folded down along the insert on the outside thereof.
The free ends of the resilient branches of the sheath are fitted beyond the insert and the washer with an annular sealing gasket, the radial projections of these branches constituting means for retaining the sleeve, the washer, and the gasket axially relative to the insert. The free ends of the branches of the sheath are externally chamfered in such a manner as to force the branches of the sheath to deflect towards one another when their ends penetrate into an associated portion of the bore of the rigid element.